An achromatic infrared (λ = 1.2–4 μm), Si-prism quarter-wave retarder (QWR) is described that uses total internal reflection at a buried Si–SiO2 interface at an angle of incidence φ near 33°, where ∂Δ/∂φ = 0. The retardance Δ deviates from 90° by <±2° within a field of view of ±10° (in air) over the entire bandwidth. Because the SiO2 layer at the base of the prism is optically thick, this QWR is unaffected by environmental contamination.
Journal of the Optical Society of America A
R. M. A. Azzam and Cristina L. Spinu, "Achromatic angle-insensitive infrared quarter-wave retarder based on total internal reflection at the Si–SiO2 interface," J. Opt. Soc. Am. A 21, 2019-2022 (2004)